1. Field of the Invention
The present invention relates to an image pick-up optical lens assembly, and more particularly, to an image pick-up optical lens assembly used in electronic products.
2. Description of the Prior Art
The demand for compact imaging lens elements has grown in recent years as the popularity of portable electronic products with the photographing function has increased, and the sensor of a general imaging lens is none other than CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor Sensor). Furthermore, as advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced, and the resolution of compact imaging lens elements has gradually increased, there is an increasing demand for compact imaging lens elements featuring better image quality.
Generally, the conventional imaging lens for portable electronic products, such as the one disclosed in U.S. Pat. No. 7,145,736, is of a triplet type comprising, in order from the object side to the image side: a first lens element with positive refractive power; a second lens element with negative refractive power; and a third lens element with positive refractive power. However, as advances in semiconductor manufacturing technology will never stop while electronic products are becoming even more compact at the same time, the pixel size of sensors will become even smaller, and the standard for image quality becomes even higher. Therefore, the three-element lens assembly has become insufficient for a high-end imaging lens module. U.S. Pat. No. 7,365,920 has disclosed a four-lens-element assembly, wherein two spherical-surface glass lens elements serving as the first and second lens elements are adhered together to form a doublet for correcting the chromatic aberration. Such an arrangement of optical elements, however, has the following disadvantages: (1) the degree of freedom of the optical system is curtailed due to the employment of excess number of spherical-surface glass lens elements, thus the total track length of the optical system cannot be reduced easily; (2) the process of adhering glass lens elements together is complicated, posing difficulties in the production process.
Therefore, a need exists in the art for an image pick-up optical lens assembly that features better image quality, higher resolution and compact size and is applicable to compact portable electronic products.